Apparatus for controlling the intensity of electrical oscillations



Aug. 27, 1935. J w MYERS 2,012,433

APPARATUS FOR CONTROLLING THE INTENSITY OF ELECTRICAL OSCILLATIONS FiledAug. '7, 1929 I N VENTOR.

A TTORNE Y.

' tube.

.Patented Aug. 27, 1935 APPARATUS FOR TENSITY, OF ELECTRICAL osoILL ToNs V J Joseph W. Myers, Jackson, Mich, assignor to i Radio Corporationof America, New York, N. Y.,

a corporation of Delaware r Application August 7, 1929, Serial No. 34,103 r I strength in the antenna.

Obviously my method may be used whenever it is desired to maintain apractical constant high frequency voltage which would otherwise besubject to changes in intensity.

In my related copending application filed April 22, 1929, Serial Number357,019, I show a method whereby an electron valve, which may be a tubeor crystal, may be caused to damp a high frequency circuit across whichit is shunted, when an unbalanced potential derived from an outputportion of the circuit is applied to the electron valve.

In this application I particularly show how a similar electron valve maybe used in series circuit, in a high frequency portion of a network anda substantially constant output obtained with a varying intensity of theinput.

I also show how my method may control regeneration in a receiver tomaintain a substantially constant output.

In the accompanying drawing:

Figure 1 is a diagrammatic view of the apparatus used when my method isapplied to a simple receiver.

Figure 2 is a similar view of the apparatus used when my method isemployed in an automatic regeneration control apparatus.

Figure 3 is a modification of the apparatus at the left of the line ze',Figure 1, whena two element vacuum tube is substituted for the crystal.

V is an electron valve, which may be a carborundum crystal, in serieswith the antenna AN and the primary L of the first R. F. transformer.

A is an R. F. amplifier and D is a detector The output of the detectormay be coupled to a conventional audio system and reproducer S.

The necessary plate supply voltages are supplied from the battery B.

As shown, R2 is a resistance in series with the cathode and battery B ofthe detector tube one of the purposes of which is for the purpose ofgetting relative grid-to-cathode bias necessary for detection by theC-bias method. The other purpose is to obtain a variable operatingvoltage.

The cathode of the detector is here connected. through an R. F. choke a;to the antenna AN to bias one of the electrodes of the electron valve,or crystal, to the same potential as the detector cathode.

V 20mins. (01. 250-420) 1: "That opposite side of the crystal V is atground potentiarof the receiver which hasbeen ad;

justed. by the potentiometer N so that'withno sig:

nail in the antenna'there will'be a small potential difference betweenthe two electrodes of 'the crystal, which, of course, will cause acurrent through the crystal, if the crystal has been placed in thecircuit in the proper manner. A crystal inserted in series with theantenna of a radio, will operate perfectly if the. crystal is given aone or two volt bias from a battery, any rectifying effect would tend toturn the alternating current into a pulsating current of the samefrequency and general characteristic as the alternating current.

This current through the crystal will cause it to have a comparativelylow resistance for any high frequency oscillations that may now come inon the antenna. The resistance of a crystal varies inversely with theapplied voltage at a very high rate. With a high plate current in D theapplied voltage would be diminished and the resistance increased. A

If now a strong signal should come in on the antenna, which is above thedesired maximum intensity, the strong signal will cause an increasedcurrent flow through detector D plate circuit, which will increase thepotential drop across R2 and this increasein potential will also applyto the antenna side of crystal V which brings it more nearly to thepotential of the other side of the crystal, and thus increases theresistance of the crystal and attenuates the current since the conductorK maintains the detector cathode, or high side of R2, and the antennaside of crystal V at the same potential.

This increase in potential tends to make the antenna terminal of thecrystal more nearly the same potential as the ground side of the crystaland thus the potential diiference that has been existent is reduced.This reduction in the potential on the crystal causes its efiectiveresistance to the high frequency signal energy coming in from theantenna to increase. Thus, less energy gets through to the amplifyingtube A and consequently the output is not permitted to be substantiallyincreased.

It is understood, of course, that there is a slight increase, since aslight increase is necessary to balance the potential on the crystal Vto an increasing degree as the signal intensity in the antennaincreases.

PATENT O CE-f1;

Thus in my system here shown V acts as a vaintensity in the antennaincreases, with a resulting substantially constant output.

In theform shown in Figure 2, T is a feed-back coil, V is a crystal andL a coupling coil for coupling the feed-back circuit to theplate circuitof the detector through its inductive coupling with L The method ofoperating is substantially the same as above described with reference toFigure 1, except the crystal V now controls feedback energy to theinput, instead of controlling energy coming in on the antenna. 7

It is obvious that as the detector output increases the resistance ofthe'crystal will increase and the feed-back will diminish.

Figure 3 shows a form of the device, in which a two element vacuum tubeis substituted for the.

crystal V. In either case whether a crystal is used or the two elementvacuum tube, as shown in Figure 3, is substituted for the crystal aslight change in the bias of the interposed part will "greatly affectthe current carrying capacity.

what I eiaimisz The combination of a circuit for an oscillating current,having an amplifier and a rectifier in said circuit, a feed-backcoupling between the delivery side of said amplifier and rectifier andthe input side of the same, an electron valve whose resistance dependsupon the potential difierential of its electrodes, said valve beingincluded in series with said feed-back circuit and means for supplyingto said valve a controlling potential that is derived from and is afunction of the output of said circuit so that it shall determine theresistance of said valve.

2; In a regenerative high frequency signalling system, having afeed-back circuit, an electron valve having an anode and a cathode inseries in said circuit, means'for biasing the anode and cathode of saidvalve to permit the passage of feed back currents, a high frequencyrectifier in said-system and connected to the electrodes of 7 said valveso as to oppose the normal biasing of said valve and to cause anincrease in its resistg0 ance upon an increase in the output of the saidsystem. r

* a JOSEPH W. MYERS.

